1. Technical Field
The present disclosure relates to surgical instruments, such as electrosurgical and ultrasonic devices, and methods for cutting tissue. More particularly, the present disclosure relates to surgical instruments that include an end-effector assembly including first and second jaw members capable of applying a combination of mechanical clamping pressure and energy to effectively seal tissue and a third jaw member disposed between the first and second jaw members configured to selectively sever tissue between the sealed tissue areas.
2. Discussion of Related Art
Electrosurgical and ultrasonic devices have become widely used by surgeons. Electrosurgery involves the application of thermal and/or electrical energy to cut, dissect, ablate, coagulate, cauterize, seal or otherwise treat biological tissue during a surgical procedure. Electrosurgery is typically performed using an electrosurgical generator operable to output energy and a handpiece including a surgical instrument (e.g., end effector) adapted to transmit energy to a tissue site during electrosurgical procedures. Electrosurgery can be performed using either a monopolar or a bipolar instrument.
The basic purpose of both monopolar and bipolar electrosurgery is to produce heat to achieve the desired tissue/clinical effect. In monopolar electrosurgery, devices use an instrument with a single, active electrode to deliver energy from an electrosurgical generator to tissue, and a patient return electrode or pad that is attached externally to the patient (e.g., a plate positioned on the patient's thigh or back) as the means to complete the electrical circuit between the electrosurgical generator and the patient. When the electrosurgical energy is applied, the energy travels from the active electrode, to the surgical site, through the patient and to the return electrode.
In bipolar electrosurgery, both the active electrode and return electrode functions are performed at the site of surgery. Bipolar electrosurgical devices include two electrodes that are located in proximity to one another for the application of current between their surfaces. Bipolar electrosurgical current travels from one electrode, through the intervening tissue to the other electrode to complete the electrical circuit. Bipolar instruments generally include end-effectors, such as grippers, cutters, forceps, dissectors and the like.
Forceps utilize mechanical action to constrict, grasp, dissect and/or clamp tissue. By utilizing an electrosurgical forceps, a surgeon can utilize both mechanical clamping action and electrosurgical energy to effect hemostasis by heating the tissue and blood vessels to cauterize, coagulate/desiccate, seal and/or divide tissue. Bipolar electrosurgical forceps utilize two generally opposing electrodes that are operably associated with the inner opposing surfaces of the end effectors and that are both electrically coupled to an electrosurgical generator. In bipolar forceps, the end-effector assembly generally includes opposing jaw assemblies pivotably mounted with respect to one another. In a bipolar configuration, only the tissue grasped between the jaw assemblies is included in the electrical circuit. Because the return function is performed by one jaw assembly of the forceps, no patient return electrode is needed.
By utilizing an electrosurgical forceps, a surgeon can cauterize, coagulate/desiccate and/or seal tissue and/or simply reduce or slow bleeding by controlling the intensity, frequency and duration of the electrosurgical energy applied through the jaw assemblies to the tissue. During the sealing process, mechanical factors such as the pressure applied between opposing jaw assemblies and the gap distance between the electrically-conductive tissue-contacting surfaces (electrodes) of the jaw assemblies play a role in determining the resulting thickness of the sealed tissue and effectiveness of the seal.
A variety of types of end-effector assemblies have been employed for various types of surgery, e.g., electrosurgery using a variety of types of monopolar and bipolar electrosurgical instruments.